Vocational and technical education programs continue to play a pivotal role in developing workers' occupational safety and health skills in all industries. The Agricultural Safety Education Initiative was first conducted in the summer of 2017 as a multi-year "Train the Trainer" program to improve teachers' tractor and machinery knowledge. The National Safe Tractor and Machinery Operations Program (NSTMOP) Curriculum was used to develop and organize the training program. The purpose of this study was to determine the efficacy of a multi-year agricultural safety education professional development model. A total of 85 teachers participated in the third year of the training program. Teachers' average NSTMOP test score was 41.9 out of 50 (SD = 3.62). Teachers attending the training for the first time in 2019 scored lower (40.8, SD = 4.41) than teachers who had attended the training during all three offerings (43.2, SD = 3.00), though the difference was not statistically significant (Kruskal-Wallis H was 5.91 (2) p = 0.052). Post-experience qualitative data findings showed many teachers reported curriculum obtainment as a motivating factor for continued attendance. A benefit expressed by teachers participating in the professional development focused on higher-order instructional and alternative assessment methods for tractor and machinery safety. For these SBAE participants, the involvement in a multi-year approach to professional development is influenced when curriculum is offered.